Silicene electronic device

ABSTRACT

A silicene electronic device includes a silicene material layer. The silicene material layer of the silicene electronic device has a 2D honeycomb structure of silicon atoms, is doped with at least one material of Group I, Group II, Group XVI, and Group XVII, and includes at least one of a p-type dopant region doped with a p-type dopant and an n-type dopant region doped with an n-type dopant. An electrode material layer including a material having a work function lower than the electron affinity of silicene is formed on the silicene material layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2018-0128534, filed on Oct. 25, 2018, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND 1. Field

The present disclosure relates to silicene electronic devices includinga silicene material layer.

2. Description of the Related Art

Silicene is a material in which silicon atoms as an allotrope form atwo-dimensional (2D) honey comb structure like graphene. Since silicenehas the same structure as graphene, silicene has a similar bandstructure to graphene and electron transport is determined by the Diracequation. Silicene is expected to have a mobility of approximately ashigh as 10⁶ cm²/Vs, and also, an electronic device (hereinafter, asilicene electronic device) including a silicene material layer isexpected to solve a physical limitation of Si devices of the relatedart. Furthermore, graphene may not use a silicon process of the relatedart, but since silicene includes silicon, an existing silicon processmay be used for manufacturing a silicene electronic device.

In a silicon-based electronic device of the related art, the forming ofan electrode plays an important role in reducing or preventing heatgeneration, reducing power consumption, and/or switching speed ofdevices. A metal-semiconductor contact is a Schottky contact, and thus,a barrier is formed. Many studies about methods of changing the Schottkycontact to an ohmic contact have been conducted. In order to change aSchottky contact to an ohmic contact, a method of reducing a Schottkycontact width (SBW) or reducing a Schottky contact height (SBH) has beenused. For example, in the related art, an ohmic contact has beenachieved by reducing the SBW by doping a Schottky contact part with ahigher concentration dopant by using an implantation method.

However, in the case of the silicene electronic device, since silicenehas a very small thickness with a single layer or a double layer, it isnot easy to form an ohmic contact by using a method of the related art.

SUMMARY

Provided are silicene electronic devices, for example, switchingdevices, such as transistors including a silicene material layer.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to an aspect of some embodiments, a silicene electronic deviceincludes: a silicene material layer having a two-dimensional (2D)honeycomb structure formed by silicon atoms, is doped with at least onematerial of Group I, Group II, Group XVI, and Group XVII, and comprisesat least one of a p-type dopant region doped with a p-type dopant and ann-type dopant region doped with an n-type dopant; and an electrodematerial layer on the silicene material layer and includes a materialhaving a work function lower than the electron affinity of silicene.

The electrode material layer may include an electride.

The electride may include a C12A7 electride, a 2D electride, and a Y₅Si₃electride.

The 2D electride may be an anisotropic 2D electrode or a polycrystalelectride. The 2D electride may include, for example, Ca₂N, Y₂C, orGd₂C.

The electrode material layer may include at least one material selectedfrom the group consisting of Mg, Ca, Y, La, and Er.

An intermediate layer may further be arranged between the silicenematerial layer and the electrode material layer. The intermediate layermay be a passivation layer or an insulating layer formed on a surface ofthe silicene material layer. The passivation layer may include Se or S.The insulating layer may include boron nitride (BN), SiO₂, or SiN. Theinsulating layer may be formed on an entire upper surface of thesilicene material layer.

The silicene electronic device may further include a graphene layerbetween the intermediate layer and the electrode material layer.

An electrode material protection layer protecting the electrode materiallayer may further be formed. The electrode material protection layer maybe a metal layer. The electrode material protection layer may cover anarea greater than an area of the electrode material layer so that sidesurfaces of the electrode material layer are not exposed to the outsideof the electrode material protection layer.

The silicene material layer may be entirely doped with at least onematerial of Group I, Group II, Group XVI, and Group XVII, and mayinclude at least one p-type dopant region and at least one n-type dopantregion.

A doping concentration of an n-type dopant in the n-type dopant regionmay be 10¹²˜10¹⁸/cm³.

A doping concentration of a p-type dopant in the p-type dopant regionmay be 10¹²˜10¹⁸/cm³.

The silicene material layer may include at least one p region doped witha p-type dopant and at least two n+ regions doped with an n-type dopanton both sides of the p region, wherein a gate electrode having a widthequal to or greater than a width of the at least one p region is formedon the p region, and a source and a drain are formed on the at least twon+ regions.

A gate insulating layer may further be formed between the gate electrodeand the silicene material layer, and a gate intermediate layer mayfurther be formed between the silicene material layer and the gateinsulating layer.

The gate intermediate layer may include one of BN, SiO₂, and SiN. Thegate intermediate layer may be formed on an entire upper surface of thesilicene material layer and may be formed as one body with theintermediate layer (insulating layer).

The silicene electronic device may further include a lower intermediatelayer provided on a lower surface of the silicene material layer.

The lower intermediate layer may include one of BN, SiO₂, and SiN.

The silicene electronic device may further include a lower gateinsulating layer and a lower gate electrode on a lower side of thesilicene material layer.

The lower gate electrode may have a width equal to or greater than awidth corresponding to the at least two n+ region and the at least one pregion of the silicene material layer.

The silicene electronic device may include a silicene material layerhaving a two-dimensional (2D) honeycomb structure formed by siliconatoms, is doped with at least one material of Group I, Group II, GroupXVI, and Group XVII, and includes a low doping concentration regionlowly doped with at least one of p-type dopant or an n-type dopant, anda high doping concentration region highly doped with at least one ofp-type dopant or an n-type dopant, and an electrode material layerformed on the high doping concentration region.

The silicene material layer may be formed as a single layer or abi-layer, and the highly doping region may be doped by substitution ofadsorption of a dopant.

The silicene material layer may include a first region formed as asingle layer or a bi-layer and a second region formed as a multilayer,and the highly doped region may be formed in the second region.

A doping concentration of the low doping concentration region may be ina range of 10¹²˜10¹⁸/cm³, and a doping concentration of the low dopingconcentration region may be in a range of 10¹⁸˜10²¹/cm³.

The silicene material layer may include a p region doped with a p-typedopant and n+ regions respectively doped with an n-type dopant on bothsides of the p region, and the highly doping region may be n+++ regionformed on a portion of the n+ region.

The silicene electronic device according to the present disclosure mayprovide a new method for forming an ohmic contact of an electrode. Forexample, a new method of forming an ohmic contact on a source and adrain of a field effect transistor (FET) of a nanometer level may beprovided.

The silicene electronic device according to the present disclosure maycontribute process simplification by reducing an implantation method.

The silicene electronic device according to the present disclosure mayprovide a dopant-free process on a contact region since an implantationprocess is simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a silicene electronic deviceincluding a silicene material layer according to some embodiments;

FIG. 2 is a plan view of the silicene electronic device of FIG. 1;

FIG. 3 is a perspective view of a silicene material layer of thesilicene electronic device of FIG. 1;

FIG. 4A is a lateral view seen from a [011] direction of restructuredSi(001);

FIG. 4B is diagram showing a case that a surface of Si(001) ispassivated with Se;

FIG. 5 is a cross-sectional view of a silicene electronic deviceincluding a silicene material layer, according to some embodiments;

FIG. 6 is a cross-sectional view of a silicene electronic deviceincluding a silicene material layer, according to some embodiments;

FIG. 7 is a cross-sectional view of a silicene electronic deviceincluding a silicene material layer, according to some embodiments;

FIG. 8 is a perspective view of a silicene material layer of thesilicene electronic device of FIG. 7;

FIG. 9 is a cross-sectional view of a silicene electronic deviceincluding a silicene material layer, according to some embodiments;

FIG. 10 is a perspective view of a silicene material layer of thesilicene electronic device of FIG. 9;

FIG. 11 is a cross-sectional view of a silicene electronic deviceincluding a silicene material layer, according to some embodiments; and

FIG. 12 is a plan view of the silicene electronic device of FIG. 11.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings. The embodiments may,however, be embodied in many different forms and should not construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the invention to those of ordinary skillin the art. The embodiments will be defined by the appended claims. Inthe entire specification, like reference numerals refer to like elementsthroughout and, in the drawings, sizes and thicknesses of constituentelements are exaggerated for clarity of explanation.

Terminology used in the specification will be briefly described and theembodiments will be described in detail.

Terminology used herein are selected as commonly used by those ofordinary skill in the art in consideration of functions of theembodiments, but may vary according to the technical intention,precedents, or a disclosure of a new technology. Also, in particularcases, some terms are arbitrarily selected by the applicant, and in thiscase, the meanings of the terms will be described in detail atcorresponding parts of the specification. Accordingly, the terms used inthe specification should be defined not by simply the names of the termsbut based on the meaning and contents of the whole specification.

It should be understood that, when a part “comprises” or “includes” anelement in the specification, unless otherwise defined, it is notexcluding other elements but may further include other elements.

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings. In this regard, theembodiments may have different forms and should not be construed asbeing limited to the descriptions set forth herein. Accordingly, theembodiments are merely described below, by referring to the figures, toexplain aspects. In the drawings, for clarity of explanation of thedisclosure, parts that are not related to the descriptions may beomitted.

FIG. 1 is a cross-sectional view of a silicene electronic device 100including a silicene material layer 110 according to some embodiments.FIG. 2 is a plan view of the silicene electronic device 100 of FIG. 1.In some embodiments, the silicene material layer 110 is formed as achannel and a transistor having a structure in which an upper gate 165and a lower gate 175 are provided.

Referring to FIGS. 1 and 2, the silicene electronic device 100 accordingto some embodiments may include the silicene material layer 110, anintermediate layer 120 on the silicene material layer 110, a graphenelayer 130 on the intermediate layer 120, an electrode material layer 140on the graphene layer 130, and/or an electrode material protection layer150 on the electrode material layer 140.

The silicene material layer 110 may be a channel of a transistor device.Referring to FIG. 3, the silicene material layer 110 may be a layer inwhich silicon atoms form a 2D honeycomb structure. Silicene of thesilicene material layer 110 may be primarily doped with at least onematerial of Group I, Group II, Group XVI, and Group XVII. For example,silicene of the silicene material layer 110 may be primarily doped withat least one material of Group I, such as Li, Na, and K, Group II, suchas Be, Mg, and Ca, and Group VII, such as F, Cl, and Br. When thesilicene material layer 110 is doped with a primarily dopant, such as amaterial of Group I, Group II, Group XVI, and Group XVII, a bandgap ofthe silicene material layer 110 may be opened and controlled. As thedoping concentration of the primarily dopant with respect to thesilicene material layer 110 increases, the bandgap of the silicenematerial layer 110 may be increased.

In a state that the silicene material layer 110 is primarily doped, asecondary doping may be performed by using a p-type dopant or an n-typedopant. For example, when the doping is performed by using animplantation method, the p-type dopant may be B or Al, and the n-typedopant may be P. Furthermore, the silicene material layer 110 may bedoped by using a substation method or an adsorption method. When thesubstation method is used, the p-type dopant may be B or Al, and then-type dopant may be N or P. When the adsorption method is used, thep-type dopant may be N, and the n-type dopant may be B or Al. However,the second dopant is not limited thereto, and a p-type dopant and ann-type dopant generally used in a semiconductor process may be used.Reference numerals 111, 112, and 113 of FIG. 3 indicate regions dopedwith second dopants, for example, reference numerals 111 and 113 may ben+-regions of the silicene material layer 110 doped with an n-typedopant, and reference numeral 112 may be p-regions doped with a p-typedopant. As another example, reference numerals 111 and 113 may bep+-regions of the silicene material layer 110 doped with a p-typedopant, and reference numeral 112 indicates an n-region doped with ann-type dopant. In this way, the silicene material layer 110 according tosome embodiments may include an NPN or PNP doping region, but thepresent embodiments are not limited thereto, and the silicene materiallayer 110 may include at least one of a p-type dopant region and ann-type dopant region.

In this way, the silicene material layer 110 according to someembodiments may have a 2D structure in which silicon atoms form ahexagonal honeycomb structure, and may be a mono-layer or a bi-layer.The silicene material layer 110 may include a double doped region inwhich both a primary doping material and a secondary doping material aredoped. The silicene material layer 110 may be doped with the primarydoping material and the secondary doping material to have respectivedoping concentrations of 10¹²˜10²¹/cm³ and 10¹²˜10¹⁸/cm² by an injectionmethod, and the primary doping material and the secondary dopingmaterial respectively substituted by silicon atoms having a hexagonalnet structure of the silicene material layer 110 or may be present as aninterstitial type dopant included between the silicon atoms. A siliconmaterial layer used in general electronic devices is in a bulk state,and a large number of silicon layers form a multi-layer structure.However, the silicene material layer 110 according to some embodimentsmay have a hexagonal 2D structure like graphene, may have a highmobility, and/or may readily control a bandgap characteristic by adoping material.

Referring to FIGS. 1 and 2, the intermediate layer 120 may include firstand second intermediate layers 121 and 122 arranged in the regions 111and 113. The intermediate layer 120 may be provided to protect thesilicene material layer 110 or to reduce or prevent the silicenematerial layer 110 from reacting with other material layers. Theintermediate layer 120 may be formed by passivating surfaces of theregions 111 and 113 with Se or S. As an example, FIG. 4A is a lateralview seen from a [011] direction of restructured Si(001), and FIG. 4B isdiagram showing a case that a surface of Si(001) is passivated with Se.The passivated intermediate layer 120 having a small thickness may beformed, for example, a thickness in a range from a single layer to fiveatom layers. In this way, since a surface of the silicene material layer110 is passivated, a dangling bond that may be present on the surface ofthe silicene material layer 110 may be removed. As another example, theintermediate layer 120 having a small thickness may be formed by usingan insulating material, such as BN, SiO₂, SiN, or TiO₂, for example, athickness in a range from a single layer to five atom layers. Forexample, BN does not change the characteristics of silicene when BNjoins with silicene. As described below, when the electrode materiallayer 140 having a low work function is used, there is a risk ofoccurring a Fermi-level pinning phenomenon in which Fermi-level is fixedto a certain level through interface states of silicon surface. However,according to some embodiments, the intermediate layer 120 is insertedbetween the silicene material layer 110 and the electrode material layer140, and thus, the formation of an interface state on the surface of thesilicene material layer 110 may be reduced or prevented and aFermi-level pinning phenomenon may be reduced or prevented. As describedbelow, when the electrode material layer 140 shows a stablecharacteristic or is silicide, the intermediate layer 120 may beomitted.

The electrode material layer 140 includes first and second electrodematerial layers 141 and 142 formed on the first and second intermediatelayers 121 and 122. The first and second electrode material layers 141and 142 may be understood as a source and a drain, respectively.

The electrode material layer 140 may be formed by using a materialhaving a low work function (hereinafter, a low work function material)lower than the electron affinity of silicene. Since the electronaffinity of silicon Si is approximately 4.05 eV, the electrode materiallayer 140 may be formed by using a material having a work function lessthan approximately 4 eV. For example, the electrode material layer 140may be formed by using a material having a work function greater thanabout 2.5 eV and less than about 3.5 eV.

For example, the electrode material layer 140 may be formed by using anelectride, such as a 12CaO₇Al₂O₃ (C12A7) electride, a 2D electride, andan Y₅Si₃ electride.

When the C12A7 electride is used as the electrode material layer 140, aTiO₂ insulating layer is generated in a process of forming the C12A7electride, and thus, the TiO₂ insulating layer may be used as theintermediate layer 120. Also, the C12A7 electride may be formed as asingle layer, and thus, may be formed by using a deposition method, forexample, sputtering.

The 2D electride may include an anisotropic 2D electride or apolycrystalline electride. The 2D electride may include Ca₂N, Y₂C, andGd₂C. The 2D electride has a high mobility in an applied-channeldirection and has a further low work function in a direction in which achannel is formed, and thus a further better ohmic contact may beobtained by forming a contact in a channel direction. Also, in the caseof the polycrystalline electride, a further lower work function may beobtained, and thus, a further better ohmic contact may be obtained.

When the Y₅Si₃ electride is used as the electrode material layer 140,Y₅Si₃ itself is already silicide, and thus, even though the electrodematerial layer 140 contacts the silicene material layer 110, additionalsilicide is not formed, and accordingly, a Schottky barrier is notgenerated. Accordingly, in this case, the intermediate layer 120 and thegraphene layer 130 may be omitted. Also, Y₅Si₃ shows stablecharacteristics in moisture and air, and thus, the electrode materialprotection layer 150 described below may be omitted.

As another example, the electrode material layer 140 may be formed byincluding a material selected from the group consisting of Mg, Ca, Y,La, and Er.

Table 1 below shows work the function of materials.

TABLE 1 Materials Work function (eV) C12A7 2.4 Ca₂N 2.6 Y₂C 2.84 Gd₂C2.85 Ca 2.87 Y 3.1 Gd 3.1 La 3.5 Mg 3.66 Hf 3.9 Al 4.28 Ti 4.33 Ni 5.15

As described above, since the silicene material layer 110 is formed as asingle layer or a double layer of silicene, when an implantation methodis used, a doping concentration of a p-type dopant or an n-type dopantmay be limited to a range of 10¹²˜10¹⁸/cm³. Thus, when a metal, such asAl, Ti, and Ni, is joined in this doping concentration, a Schottkybarrier may be formed. The relationships between the Schottky barrier,work function, and electron affinity are as follows. As shown inEquation 1, when a work function of a material that formed the electrodematerial layer 140 is lower than the electron affinity of silicene, aSchottky barrier may be substantially disappeared, and accordingly, theelectrode material layer 140 may form an ohmic contact with the silicenematerial layer 110.ϕ_(B)=ϕ_(M) −X  [Equation 1]

Here, ϕ_(B) indicates Schottky barrier, ϕ_(M) indicates work function,and X indicates electron affinity.

Also, when the size of the silicene electronic device 100 is in a nmlevel, an implantation concentration may not be uniform, and thus, theformation of an ohmic contact may be difficult. However, since a highdoping concentration region (for example, an N+++ region) is notrequired by forming the ohmic contact using a material having a workfunction lower than silicene, and thus, an implantation process issimplified and a dopant-free process in the joining region may beprovided.

Furthermore, to realize a Fin FET in which a silicene material layer isused as a channel layer, the doping of silicene may be difficult byusing virtually the implantation method due to the very small thicknessof the silicene. However, the forming of an ohmic contact by using amaterial having a low work function allows the manufacturing of the FinFET to be easier.

The graphene layer 130 may include first and second graphene layers 131and 132 formed on the first and second intermediate layers 121 and 122.The graphene layer 130 may include a single layer. The graphene layer130 may reduce or prevent oxidation of the silicene material layer, andalso, may additionally reduce a work function of the silicene materiallayer. Table 2 below shows work functions with respect to Ca₂N(001),MLG/Ca₂N(001), and BLG/Ca₂N(001). Referring to Table 2, it is seen thata work function is further reduced since the graphene layer 130 and theelectrode material layer 140 have a double layer structure.

TABLE 2 Materials Work function (eV) Ca₂N 3.39, 3.43, 3.5 MLG/Ca₂N 2.95BLG/Ca₂N 3.47 MLG 3.94, 4.26 BLG 3.97, 4.28

Also, since graphene is a 2D material like silicene, it is easy to formthe graphene layer 130 on the silicene material layer 110. When theelectrode material layer 140 is very stable or has a sufficiently lowwork function, the graphene layer 130 may be omitted.

The electrode material protection layer 150 is formed on the electrodematerial layer 140. The electrode material protection layer 150 mayinclude first and second electrode material protection layers 151 and152 covering the first and second electrode material layers 141 and 142,respectively. The electrode material protection layer 150 reduces orprevents the electrode material layer 140 from oxidation. The electrodematerial protection layer 150 may include a metal. The electrodematerial protection layer 150 may be formed not to expose sides of theelectrode material layer 140 by depositing a metal on a region greaterthan an area of the electrode material layer 140. As another example,when the electrode material layer 140 shows a stable characteristic likeY₅Si₃, the electrode material protection layer 150 may be deposited onan upper surface of the electrode material layer 140 or the electrodematerial protection layer 150 may be omitted.

An upper gate intermediate layer 161, an upper gate insulating layer163, and/or an upper gate electrode 165 may be formed on a regionbetween regions where the first and second electrode material layers 141and 142 are formed. A lower intermediate layer 171, a lower gateinsulating layer 173, and a lower gate electrode 175 may be formed on alower side of the silicene material layer 110.

The upper gate intermediate layer 161 and the lower intermediate layer171 are selectively formed to protect the silicene material layer 110 orto reduce or prevent the silicene material layer 110 from reacting withother material layers. The upper gate intermediate layer 161 and thelower intermediate layer 171 may be formed by using a material having alow reactivity with the silicene material layer 110, for example, aninsulating material such as, boron nitride (BN), SiO₂, and SiN, and asthin as possible in a thickness range from a single layer to five atomlayers

The upper and lower gate insulating layers 163 and 173 may includesilicon oxide or a high-k material having a dielectric constant greaterthan the silicon oxide. For example, the upper and lower gate insulatinglayers 163 and 173 may include silicon oxide, such as SiO₂, a siliconnitride, such as Si₃N₄, aluminum oxide, zirconium oxide, hafnium oxide,etc.

The upper and lower gate electrodes 165 and 175 may include a conductivematerial, that is, a material that is used as an electrode material inelectronic devices, for example, conductive metal oxide, conductivenitride oxide, and a conductive polymer may be used without limitation.The upper gate electrode 165 may be formed on a region corresponding toa central part of the silicene material layer 110, for example, when thesilicene material layer 110 includes an NPN doping region, the uppergate electrode 165 may be formed on a region corresponding to the region112 which is region doped with a p-type dopant. When the silicenematerial layer 110 includes an NPN doping region, the upper gateelectrode 165 may have a width equal to or a slightly greater than awidth of the p-type doping region (the region 112). When the silicenematerial layer 110 includes a PNP doping region, the upper gateelectrode 165 may have a width equal to or a slightly greater than awidth of the n-type doping region. The lower gate electrode 175 may beformed to have a width greater than that of the upper gate electrode165. That is, when the silicene material layer 110 is doped of an NPNtype or a PNP type, the upper gate electrode 165 is formed to havesubstantially equal to or similar to a central doping region (the region112), but the lower gate electrode 175 may be formed to have a widthcorresponding to both the NPN type or the PNP type doping regions of thesilicene material layer 110.

A primary doping is performed by using a material like an alkali metalto open a band gap of the silicene material layer 110. In the doping ofthe silicene material layer 110 with an alkali metal, theoretically, aband gap of silicene may be present at a lower position than a Fermilevel. Therefore, a whole chemical potential of the silicene materiallayer 110 is moved by applying a voltage to the lower gate electrode 175so that the Fermi level is located between the band gap, and thus, thesilicene material layer 110 may have a semiconductor characteristic.When a voltage is applied to the upper gate electrode 165, a channel isformed.

FIG. 5 is a cross-sectional view of a silicene electronic device 200including a silicene material layer 110 according to some embodiments.

Referring to FIG. 5, the silicene electronic device 200 according tosome embodiments is substantially identical to the silicene electronicdevice 100 described with reference to FIGS. 1 through 4 except that agate electrode 265 is formed only on the silicene material layer 110,and thus, only the differences will be described.

The silicene electronic device 200 may include a silicene material layer110 on a lower structure 273, an intermediate layer 120 on the silicenematerial layer 110, a graphene layer 130 on the intermediate layer 120,an electrode material layer 140 on the graphene layer 130, and/or anelectrode material protection layer 150 on the electrode material layer140. The intermediate layer 120 may include first and secondintermediate layers 121 and 122 formed on regions 111 and 113. Theelectrode material layer 140 may include first and second electrodematerial layers 141 and 142 formed on the first and second intermediatelayers 121 and 122. The first and second electrode material layers 141and 142 may be understood as a source and a drain, respectively. A gateintermediate layer 261, a gate insulating layer 263, and a gateelectrode 265 may be formed on a region between regions where the firstand second electrode material layers 141 and 142 are formed. A lowerintermediate layer 271 may be formed between the lower structure 273 andthe silicene material layer 110.

The lower structure 273 may include a material layer used as a substrateof a general electronic device, and also, may include the same materialas the gate intermediate layer 261.

The gate intermediate layer 261 and the lower intermediate layer 271 maybe selectively formed to protect the silicene material layer 110 or toreduce or prevent the silicene material layer 110 from reacting withother material layers. The gate intermediate layer 261 and the lowerintermediate layer 271 may be formed by using a material having a lowreactivity with the silicene material layer 110, for example, aninsulating material, such as BN, SiO₂, and SiN, and as thin as possiblein a thickness range from a single layer to five atom layer. When thelower structure 273 includes a material layer including the samematerial as the gate intermediate layer 261, the lower intermediatelayer 271 may be omitted.

The gate insulating layer 263 may include a high-k material having adielectric constant greater than silicon oxide or nitride oxide. Forexample, the gate insulating layer 263 may include silicon oxide, suchas SiO₂, silicon nitride, such as Si₃N₄, aluminum oxide, zirconiumoxide, hafnium oxide, etc.

The gate electrode 265 may include a conductive material, for example,any material, for example, a metal, a conductive metal oxide, aconductive metal nitride, a conductive polymer, etc. that is used as anelectrode material in an electronic device. The gate electrode 265 maybe formed on a region corresponding to a central region of the silicenematerial layer 110. For example, when the silicene material layer 110includes an NPN doping region, the gate electrode 265 may be formed on aregion corresponding to a region 112 which is a p-type doping region.When the silicene material layer 110 includes an NPN doping region, thegate electrode 265 may be formed to have a width equal to or slightlygreater than a width of the p-type doping region (region 112). Also,when the silicene material layer 110 includes a PNP doping region, thegate electrode 265 may be formed to have a width equal to or slightlygreater than a width of the n-type doping region. The gate electrode 265may control a chemical potential of the silicene material layer 110. Inparticular, when the silicene material layer 110 includes a PNP dopingregion or an NPN doping region, the gate electrode 265 may control achemical potential of the region 112, which is an n-type doping regionor a p-type doping region.

FIG. 6 is a cross-sectional view of a silicene electronic device 300including a silicene material layer 110, according to some embodiments.

Referring to FIG. 6, the silicene electronic device 300 according tosome embodiments is substantially identical to the silicene electronicdevice 100 described with reference to FIGS. 1 through 5 except that anupper intermediate layer 320 is formed on entire upper region of thesilicene material layer 110, and thus, only the differences will bedescribed.

The upper intermediate layer 320 is formed on an entire upper region ofthe silicene material layer 110 to protect the silicene material layer110 or to reduce or prevent the silicene material layer 110 fromreacting with other material layers. The upper intermediate layer 320may be formed as thin as possible using an insulating material, such asBN, SiO2, and SiN, for example, in a thickness range from a single layerto five atom layers. For example, BN does not change characteristics ofsilicene by joining with silicene. The upper intermediate layer 320protects the silicene material layer 110, and furthermore, since theupper intermediate layer 320 is located between the silicene materiallayer 110 and the electrode material layer 140, the formation of aninterface state on a surface of the silicene material layer 110 may bereduced or prevented.

FIG. 7 is a cross-sectional view of a silicene electronic device 400including a silicene material layer 410 according to another embodiment.FIG. 8 is a perspective view of the silicene material layer 410 of thesilicene electronic device 400 of FIG. 7.

Referring to FIGS. 7 and 8, the silicene electronic device 400 accordingto some embodiments includes a silicene material layer 410, and firstand/or second electrode material layers 420 and 430 on the silicenematerial layer 410. An upper gate intermediate layer 161, an upper gateinsulating layer 163, and/or an upper gate electrode 165 may be formedon a region of the silicene material layer 410 between regions where thefirst and second electrode material layers 420 and 430 are formed. Alower intermediate layer 171, a lower gate insulating layer 173, and alower gate electrode 175 may be formed on a lower side of the silicenematerial layer 410.

The silicene material layer 410 may be a channel of a transistor device.As described above, a band gap of the silicene material layer 410 may beopened and controlled by primarily doping the silicene material layer410 with at least one material of Group I, Group II, Group XVI, andGroup XVII. Also, in a state that the silicene material layer 410 isprimarily doped, a secondary doping of the silicene material layer 410with a p-type dopant or an n-type dopant may be performed by using animplantation method. The p-type dopant may be B, Al, etc. and the n-typedopant may be P, etc. The secondary doping may be performed so that thesilicene material layer 410 has a doping concentration of 10¹²˜10¹⁸/cm³with a second dopant. Furthermore, a tertiary doping may be performed byusing a substitution method or an adsorption method on a portion of theregion where the secondary doping is performed, and thus, a dopingconcentration of the tertiary doped region doped with a p-type dopant oran n-type dopant may be increased to 10¹⁸˜10²¹/cm³. When thesubstitution method is used, the p-type dopant may be B, Al, etc. andthe n-type dopant may be N, P, etc. When adsorption method is used, thep-type dopant may be N, and the n-type dopant may be B, Al, etc.However, dopants for the secondary and tertiary doping are not limitedthereto, and any p-type dopant or n-type dopant that is generally usedin a semiconductor process may be used.

Reference numerals 411 and 415 in FIG. 8 indicate tertiary doped highlydoped regions, and reference numerals 412, 413, and 414 indicatesecondary doped low doped regions. For example, reference numerals 411and 415 indicate n+++ regions of the silicene material layer 410 highlydoped with an n-type dopant, reference numerals 412 and 414 indicate n+regions of the silicene material layer 410 doped with an n-type dopant,and reference numeral 413 indicates a p region of the silicene materiallayer 410 doped with a p-type dopant. As another example, referencenumerals 411 and 415 indicate p+++ regions highly doped with a p-typedopant, reference numerals 412 and 414 indicate p+ regions of thesilicene material layer 410 doped with a p-type dopant, and referencenumeral 413 indicates an n region of the silicene material layer 410doped with an n-type dopant.

The first and second electrode material layers 420 and 430 are formed onthe highly doped regions 411 and 415, respectively, of the silicenematerial layer 410. For example, when reference numerals 411, 412, 413,414, and 415 are an n+++ region, an n+ region, a p region, an n+ region,and an n+++ region, respectively, the first electrode material layer 420may be located between a portion of the n+ region 412 and the n+++region 411, the upper gate intermediate layer 161 may be located betweena portion of the n+ regions 412 and 414 and the p region 413, and thesecond electrode material layer 430 may be located between a portion ofthe n+ region 414 and the n+++ region 415. The first and secondelectrode material layers 420 and 430 may include a metal material usedin a source or drain of the related art. An area of the first electrodematerial layer 420 may be equal to or greater than an area of the highlydoped region 411, an area of the second electrode material layer 430 maybe equal to or greater than the highly doped region 415. The first andsecond electrode material layers 420 and 430 respectively may beunderstood as a source and a drain.

As described above, the silicene material layer 410 according to someembodiments is doped with a dopant by using a substitution method or anadsorption method, and thus, the silicene material layer 410 may behighly doped with a concentration of 10¹⁸˜1021/cm³. Therefore, althoughan electrode material used in a source or a drain of the related art isused in the silicene material layer 410, a height of a Schottky barrieris reduced, and as a result, an ohmic contact may be formed.

FIG. 9 is a cross-sectional view of a silicene electronic device 500including a silicene material layer 510, according to some embodiments.FIG. 10 is a perspective view of the silicene material layer 510 of thesilicene electronic device 500 of FIG. 9.

Referring to FIGS. 9 and 10, the silicene electronic device 500according to some embodiments may include the silicene material layer510 and first and second electrode material layers 520 and 530 on thesilicene material layer 510. An upper gate intermediate layer 161, anupper gate insulating layer 163, and/or an upper gate electrode 165 maybe formed on a region of the silicene material layer 510 between regionswhere the first and second electrode material layers 520 and 530 areformed. A lower intermediate layer 171, a lower gate insulating layer173, and/or a lower gate electrode 175 may be formed on a lower side ofthe silicene material layer 510.

The silicene material layer 510 may be a channel of a transistor device.The silicene material layer 510 may have a 2D structure in which siliconatoms form a hexagonal honeycomb structure, and except for a region ofthe silicene material layer 510, a remaining region may have a singlelayer structure or a bi-layer structure. Some regions of the silicenematerial layer 510 may be a multilayer of silicene. The silicenemultilayer may include, for example, more than three layers.

As described above, a band gap of the silicene material layer 510 may beopened and controlled by primarily doping the silicene material layer510 with at least one material of Group I, Group II, Group XVI, andGroup XVII. Also, in a state that the silicene material layer 510 isprimarily doped, a secondary doping of the silicene material layer 510with a p-type dopant or an n-type dopant may be performed by using animplantation method. The p-type dopant may be B, Al, etc. and the n-typedopant may be P, etc. However, dopants for the secondary doping are notlimited thereto, and any p-type dopant or n-type dopant that isgenerally used in a semiconductor process may be used.

In FIG. 10, reference numerals 511 and 515 indicate regions of thesilicene material layer 510 where silicene multilayers are formed, andreference numerals 512 and 513 indicate regions of the silicene materiallayer 510 where a silicene single layer or a silicene double layer isformed. When a region of the silicene material layer 510 is formed as asilicene single layer or a silicene bi-layer, and when a secondarydoping is performed by using an implantation method, due to a smallthickness of silicene, a doping concentration of a secondary dopant maybe limited to approximately 10¹²˜10¹⁸/cm³. A region of the silicenematerial layer 510 is formed as a silicene multilayer, and the dopingconcentration of the secondary dopant may be increased to 10¹⁸˜10²¹/cm³.Accordingly, in FIG. 10, regions of reference numerals indicate highlydoped regions, and reference numerals 512, 513, and 514 indicate lowdoped regions. For example, regions of the silicene material layer 510indicated by reference numerals 511 and 515 may be n+++ regions highlydoped with an n-type dopant, regions indicated by reference numerals 512and 514 may be n+ regions doped with an n-type dopant, and a regionindicated by reference numeral 513 may be a p region doped with a p-typedopant. As another example, the regions of the silicene material layer510 indicated by reference numerals 511 and 515 may be p+++ regionshighly doped with a p-type dopant, the regions indicated by referencenumerals 512 and 514 may be p+ regions doped with a p-type dopant, andthe region indicated by reference numeral 513 may be an n region dopedwith an n-type dopant.

The first and second electrode material layers 520 and 530 respectivelyare formed on the highly doped regions 511 and 515 of the silicenematerial layer 510. When reference numerals 511, 512, 513, 514, and 515respectively are an n+++ region, an n+ region, a p region, an n+ region,and an n+++ region, the first electrode material layer 520 may belocated between a portion of the n+ region 512 and the n+++ region 511,the upper gate intermediate layer 161 may be located between portions ofthe n+ regions 512 and 514 and the p region 513, and the secondelectrode material layer 530 may be located between a portion of the n+region 514 and the n+++ region 515.

The first and second electrode material layers 520 and 530 may includeany material that is used as an electrode material in an electronicdevice, such as a metal, a conductive metal oxide, a conductive metalnitride, a conductive polymer, etc. An area of the first electrodematerial layer 520 may be equal to or greater than the area of thehighly doped region 511, and an area of the second electrode materiallayer 530 may be equal to or greater than the area of the highly dopedregion 515. The first and second electrode material layers 520 and 530respectively may be understood as a source and a drain.

As described above, in the silicene material layer 510 according to someembodiments, a region of the silicene material layer 510 for forming anohmic contact is formed as a silicene multilayer, and thus, a dopingconcentration of 10¹⁸˜10²¹/cm³ may be achieved by using an implantationmethod. Also, although an electrode material used in a source or drainof the related art is used as it is, a height of a Schottky barrier maybe reduced, and thus, an ohmic contact may be formed.

FIG. 11 is a cross-sectional view of a silicene electronic device 600including a silicene material layer 610 according to some embodiments;and FIG. 12 is a plan view of the silicene electronic device 600 of FIG.11.

Referring to FIGS. 11 and 12, the silicene electronic device 600according to some embodiments may include the silicene material layer610 on a lower structure 673, an intermediate layer 620, a graphenelayer 630, an electrode material layer 640, and/or an electrode materialprotection layer 650.

The lower structure 673 may include a material layer used as a substrateof a general electronic device, and also, may be a material layer formedof the same material as a gate intermediate layer

A band gap of the silicene material layer 610 may be opened andcontrolled by primarily doping the silicene material layer 610 with atleast one material of Group I, Group II, Group XVI, and Group XVII. Aregion of the silicene material layer 610 may be secondary doped with ap-type dopant or an n-type dopant. For example, a first doping region611 of the silicene material layer 610 may be a region doped with one ofp-type dopant and an n-type dopant, and a second doping region 613 maybe a region doped with a dopant having a polarity different from that ofthe first doping region 611. For example, when the first doping region611 is a region doped with a p-type dopant, the second doping region 613may be a region doped with an n-type dopant. Also, when the first dopingregion 611 is a region doped with an n-type dopant, the second dopingregion 613 may be a region doped with a p-type dopant.

The intermediate layer 620 may include first and second intermediatelayers 621 and 622 provided on the first and second doping regions 611and 613, respectively. The intermediate layer 620 may be provided toprotect the intermediate layer 620 or to reduce or prevent theintermediate layer 620 from reacting with other material layers. Theintermediate layer 620 may be formed by passivating surfaces of theregions 111 and 113 of the silicene material layer 110 or by using aninsulating material, such as BN, SiO₂, and SiN, and may be formed as athickness range from a single to a five atom layer.

The graphene layer 630 may include first and second graphene layers 631and 632 formed on the first and second intermediate layers 621 and 622.The graphene layer 630 may include a single layer. The graphene layer630 may reduce or prevent oxidation, and additionally, may furtherreduce work function. Also, since graphene is a 2D material likesilicon, the graphene layer 630 may be readily formed on the silicenematerial layer 610.

The electrode material layer 640 may include first and second electrodematerial layers 641 and 642 formed on the first and second graphenelayers 631 and 632. The first and second electrode material layers 641and 642 may be understood as a source and a drain, respectively. Theelectrode material layer 640 may include a material having a workfunction less than the electron affinity of silicon Si. The electronaffinity of silicon Si is approximately 4.05 eV, and thus, the electrodematerial layer 640 may include a material having a work function lessthan approximately 4 eV. For example, the electrode material layer 640may include an electride, such as a C12A7 electride, a 2D electride, anda Y₅Si₃ electride. As another example, the electrode material layer 640may include at least one material selected from the group consisting ofMg, Ca, Y, La, and Er.

The silicene electronic device 600 may further include an electrodematerial protection layer 650. The electrode material protection layer650 may include first and second electrode material protection layers651 and 652 covering the first and second electrode material layers 641and 642, respectively.

Some or all of the intermediate layer 620, the graphene layer 630, andthe electrode material protection layer 650 may be omitted depending onan electrode material of the embodiments described above.

In the silicene electronic device 600 shown in FIGS. 11 and 12, thesilicene material layer 610 includes a first doping region 611 and asecond doping region 613, and an intermediate region 612 may be formedbetween first and second doping regions 611 and 613. An electric devicehaving the structure may be a diode type electronic device.

While embodiments of silicene electronic devices have been describedwith reference to the figures, it will be understood by those ofordinary skill in the art that various changes in form and details maybe made therein without departing from the spirit and scope as definedby the following claims.

What is claimed is:
 1. A silicene electronic device comprising: asilicene material layer having a two-dimensional (2D) honeycombstructure formed by silicon atoms, doped with at least one material ofGroup I, Group II, Group XVI, and Group XVII, and comprises at least oneof a p-type dopant region doped with a p-type dopant and an n-typedopant region doped with an n-type dopant; and an electrode materiallayer on the silicene material layer and includes a material having awork function lower than an electron affinity of silicene, wherein theelectrode material layer comprises an electride.
 2. The siliceneelectronic device of claim 1, wherein the electride comprises a C12A7electride, a 2D electride, and a Y₅Si₃ electride.
 3. The siliceneelectronic device of claim 1, further comprising an electrode materialprotection layer protecting the electrode material layer.
 4. Thesilicene electronic device of claim 3, wherein the electrode materialprotection layer covers an area greater than an area of the electrodematerial layer so that sides of the electrode material layer are notexposed to the outside of the electrode material protection layer. 5.The silicene electronic device of claim 1, wherein the silicene materiallayer is entirely doped with at least one material of Group I, Group II,Group XVI, and Group XVII, and comprises one p-type dopant region andone n-type dopant region.
 6. The silicene electronic device of claim 1,wherein a doping concentration of the n-type dopant in the n-type dopantregion is 10¹²˜10¹⁸/cm³.
 7. The silicene electronic device of claim 1,wherein a doping concentration of the p-type dopant in the p-type dopantregion is 10¹²˜10¹⁸/cm³.
 8. The silicene electronic device of claim 1,wherein the silicene material layer comprises at least one p regiondoped with a p-type dopant and at least two n+ regions, doped with ann-type dopant on both sides of the at least one p region, wherein a gateelectrode having a width equal to or greater than a width of the atleast one p region is on the at least one p region, and a source and adrain are on the at least two n+ regions.
 9. The silicene electronicdevice of claim 8, further comprising a lower intermediate layer on alower surface of the silicene material layer.
 10. The siliceneelectronic device of claim 9, wherein the lower intermediate layerincludes one of BN, SiO₂, and SiN.
 11. The silicene electronic device ofclaim 9, further comprising a lower gate insulating layer and a lowergate electrode on a lower side of the silicene material layer.
 12. Thesilicene electronic device of claim 11, wherein the lower gate electrodehas a width equal to or greater than a width corresponding to the atleast two n+ region and the at least one p region of the silicenematerial layer.
 13. A silicene electronic device comprising: a silicenematerial layer having a two-dimensional (2D) honeycomb structure formedby silicon atoms, doped with at least one material of Group I, Group II,Group XVI, and Group XVII, and comprises at least one of a p-type dopantregion doped with a p-type dopant and an n-type dopant region doped withan n-type dopant; and an electrode material layer on the silicenematerial layer and includes a material having a work function lower thanan electron affinity of silicene, wherein the electrode material layercomprises at least one material selected from the group consisting ofCa, Y, La, and Er.
 14. A silicene electronic device comprising: asilicene material layer having a two-dimensional (2D) honeycombstructure formed by silicon atoms, doped with at least one material ofGroup I, Group II, Group XVI, and Group XVII, and comprises at least oneof a p-type dopant region doped with a p-type dopant and an n-typedopant region doped with an n-type dopant; an electrode material layeron the silicene material layer and includes a material having a workfunction lower than an electron affinity of silicene; and anintermediate layer between the silicene material layer and the electrodematerial layer.
 15. The silicene electronic device of claim 14, whereinthe intermediate layer comprises a passivation layer or an insulatinglayer on a surface of the silicene material layer.
 16. The siliceneelectronic device of claim 15, wherein the passivation layer comprisesSe or S.
 17. The silicene electronic device of claim 15, wherein theinsulating layer comprises boron nitride (BN), SiO₂, or SiN.
 18. Thesilicene electronic device of claim 15, wherein the insulating layer ison an entire upper surface of the silicene material layer.
 19. Thesilicene electronic device of claim 15, further comprising a graphenelayer between the intermediate layer and the electrode material layer.